The Foucault Pendulum has long been one of the most memorable areas of the Museum, even if some people (this girl) lack the patience to actually watch the pendulum kick over a peg.

When a peg does go over, there are inevitable cheers. As the pendulum swings, it moves clockwise with the Earth’s rotation, knocking over one peg approximately every 15 minutes. Although the pendulum appears to be traveling around the circle, it’s actually the earth that moves, making this exhibit a perfect visualization of the earth’s rotation.

(Foucault himself said it a little less simply, like this: T = 24/sin q where T equals the amount of time to make one complete revolution and q is the latitude of the pendulum.)

We scoured the interwebs (as we are wont to do) to gather some of our favorite photos of patrons standing enrapt around the pendulum.

When you walk into the Wiess Energy Hall, the very first thing you see is our Foucault pendulum.

It is a metal ball suspended by a cable that swings back and forth encircled by pegs. Children and adults will run through the rest of the museum, reach the pendulum, and wait with baited breath to watch a peg topple. When one of the pegs finally falls, you can hear a cheer erupt from the area. It is one of the most memorable parts of the museum. As the pendulum swings, it moves clockwise knocking down pegs as the Earth turns. It swings back and forth, back and forth (you are getting sleepy).

Foucault Pendulum at the Houston Museum of Natural Science

It is interesting to sit around the pendulum and listen to people try to explain it.

Some will talk about how it is a clock. Others will put the time between pegs being knocked down between 10 minutes and 1 hour. Our pendulum knocks down a peg on an average of every fifteen minutes. While the pendulum looks like it rotates around the circle, it is the Earth that is rotating and the pendulum that just swings. The pendulum is a visualization of a rotating Earth. To describe it in a different way, T = 24/sin q where T equals the amount of time to make one complete revolution and q is the latitude of the pendulum. At least that’s what Foucault said.

Leon Foucault was born in Paris (France, not Texas) on September 18, 1819.

As a young boy he did not show an inclination towards science or study. In fact his teacher considered him lazy because he did not turn in his work. He did, however, enjoy building mechanical devices, such as a small steam engine and a telegraph, and tinkering. He entered medical school to become a surgeon, but found that he fainted at the sight of blood. Instead of becoming a blindfolded surgeon, he switched to physics.

At the age of 25, not having learnt anything at school nor from book, enthusiastic about science but not about study, Léon Foucault took on the task of making the work of scientists understandable to the public and of passing judgment on the value to the work of leading men of science – J Bertrand, Éloge historique de Léon Foucault.

Foucault proved his worth in being able to take mathematical proofs and construct a mechanical proof, his pendulum being one of those.

He also constructed a device to prove that light moves slower through water than air. The mathematics describing the proof had been around for over a decade, but Foucault was the first to prove that it worked. His first pendulum on public display opened on February 3, 1851 in the Paris Observatory (again France, not Texas). Instead of knocking down pins as the pendulum moved, the first Foucault pendulum drew in sand. He also invented the gyroscope, which stays in place as the Erath moves around it. This invention has proved essential for planes, space craft, and even the Hubble Telescope.

After he came to power, Napoleon III, an amateur scientist, created a job for Foucault at the newly named Imperial Observatory. There, Foucault developed his knife edge test to measure the conic shape of mirrors. This led to a more constant quality of lenses for use in telescopes. He died on February 11, 1868 from multiple sclerosis. His legacy lives on today. He has an asteroid named in his honor. But he is honored around the world by his plethora of pedula that swing to and fro, showing people that the Earth keeps on spinning.